A landmark government health study released last week provides evidence that the diesel engine exhaust that pervades California highways could be causing cancer at a greater rate than previously known.
The study says miners exposed to diesel engine exhaust are three times more likely to contract lung cancer and die, and that a similar increased risk applies to people from smoggy, urban areas such as Southern California who live near freeways or commute to work.

The long-term study, carried out by the National Cancer Institute and the National Institute for Occupational Safety and Health, is described by scientists and advocacy groups as the most thorough study on the topic ever released. The study was published in the current edition of the Journal of the National Cancer Institute.

The data will be examined by the International Agency for Research on Cancer, part of the World Health Organization, at the agency’s meeting in June to decide if diesel exhaust should be re-classified as a known carcinogen. Now, exhaust from diesel trucks, buses, portable generators and off-road construction equipment is classified as a “probable carcinogen.”

In California, studies of exposure to diesel exhaust along freeway corridors and inside cars on truck-congested freeways led the California Air Resources Board in 1998 to classify diesel particulate matter as a toxic air contaminant.

The latest ground-breaking study could lead to even tighter regulations

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on buses, trucks, locomotives, ships and other sources of black soot emitted into the air and breathed by 16 million Southern Californians.
“The more we find out about diesel exhaust, the more we are aware of its dangers to the public,” said Dimitri Stanich, a spokesman for CARB in Sacramento.

Martin Schlageter, campaign director for the nonprofit Coalition for Clean Air in Los Angeles, said the findings are frightening.

“This is not a three-fold increase in gray hair. It’s in lung cancer and death,” he said. “Every time a study comes out (on diesel emissions), it is even more toxic than what we thought. But the message is the same: Dirty diesel kills.”

In the San Gabriel Valley and Inland Empire, trucks on freeways are increasing, experts said. The Southern California Association of Governments (SCAG)’s Regional Transportation Plan estimates freight traffic – mostly by diesel trains and diesel trucks – will double in the region by 2032.

“If you live near the 60, or the 710, or the 605, you will have double the truck traffic,” Schlageter said.

SCAG has proposed a double-decker truck lane near the 60 Freeway between the 605 and 57 freeways, but only if the trucks that use it are zero emission. Those trucks would have to run on batteries, hydrogen-powered fuel cells or some type of overhead electrical power like a light-rail trolley, according to the RTP.

The study looked at 20 years of real data on miners exposed to diesel exhaust.

The authors of the study “make the leap” from the 12,000 miners to millions of urban Americans, said Bruce Hill, a scientist studying diesel emissions with the Clean Air Task Force, a group advocating for clean fuels and against coal-fired power plants.

“(The) findings suggest that the risks may extend to other workers exposed to diesel exhaust in the United States and abroad, and to people living in urban areas where diesel exhaust levels are elevated,” said Joseph Fraumeni Jr., director of the National Cancer Institute’s Division of Cancer Epidemiology and Genetics, which conducted the study, in a statement.

The study showed statistically significant increases in the risk of lung cancer mortality among underground workers as the level of diesel exposure increased, especially in those who worked for more than five years.

It concludes that the risk of dying from lung cancer was three times higher for those directly exposed to diesel exhaust than those exposed to lower doses of diesel exhaust, Hill said. Hill estimated those exposed to only 2 to 6 micrograms of diesel pollution over a lifetime – a much lower dose than received by the miners and a possible dose for urban dwellers

Diesel trucks travel the 60 Freeway through Hacienda Heights March 7, 2012. Diesel emissions are more dangerous than previously thought. Some say even commuters riding on the freeway can breathe in diesel exhaust and get exposure levels that cause cancer and premature death. (SGVN/Staff photo by Leo Jarzomb)
- would increase their risk of getting lung cancer by 50 percent.
“In some of the big cities, there may well be levels that reach that,” he said.

Hill’s own studies in Los Angeles County between 2003 and 2009 found that some levels of diesel exhaust exist in varying amounts on and near freeways, whether inside a diesel-powered school bus, a car on the freeway, or in the air in a neighborhood next to a freeway.

Drivers are exposed to higher concentrations than people standing on the sidewalk alongside a freeway due to the “wind tunnel” effect, Stanich said.

“If you are driving in L.A. every day and you are in traffic with diesel exhaust, you will get high exposures to these pollutants,” Hill said.

From his studies of diesel pollution inside cars riding in tunnels in Boston and other cities, he said keeping the car windows up will cut way back on exposure. Also, punching your car’s “recirculate” button will keep out harmful exhaust.

A HEPA filter in a car traps the fine particles that measure 2.5 microns or smaller. These can lodge deep into the lungs and even enter the blood system, Stanich explained.

Also helping reduce exposure are CARB’s regulatory programs launched in 2000 with the goal of cutting airborne diesel particulate matter by 80 percent by 2020, Stanich said. CARB is supplying grants to help trucking companies replace fleets with newer, cleaner truck models or retrofit them with particulate traps. Also, sulphur has been removed from diesel fuel.

“A diesel truck sold today is more than 90 percent cleaner than one sold 20 years ago,” Stanich said.

Dennis Firestone, president/CEO of KKW Trucking, Inc. in Pomona, said he has been attacking the problem of exposure to diesel in two ways: buying cleaner tractors and reducing fuel use.

The Pomona-based company has about 350 trucks that transport in several western states. The average age of his fleet is 1 1/2 years old, he said, due to an aggressive replacement plan.

Recently, ACE Beverage Co. of Boyle Heights replaced 25 old trucks with brand new ones, with the help of a grant from the South Coast Air Quality Management District. AQMD said the trucks are 96 percent cleaner.

“There has been a significant reduction of emissions over the last decade,” Firestone said. “So the danger is diminishing rapidly. That’s the good news.”

He also reduces fuel used by KKW trucks by prohibiting idling in the truck yard and by participating in a U.S. EPA program that helps trucks yield better mileage through add-on devices such as “belly skirts” that increase aerodynamics.

The NCI study uses 20 years of real data to gauge the risk of diesel exposure on miners, making it extremely valuable to scientists. However, its results were suppressed by mining and diesel-truck manufacturing lobbies since the late 1990s.

The House Committee on Education and the Workforce and the federal courts allowed these industries to review the study results before they could be published. The agencies that performed the study fall under the Department of Health and Human Services (HHS).

Recently, HHS appealed the court order and went ahead and published the study results, according to The Center for Public Integrity, which had pushed for publication.